122 PROCEEDINGS OF THE ACADEMY OF 



of Conlfera are mostly adherent to the branches, and that the degree of adhe- 

 sion is in exact proportion to specific or i?idividual vigor. I believe I can now 

 show that the production of the sexes is influenced by the same law, — that a 

 high stage of vitality, or vigor, is favorable to the production of female 

 flowers ; and a low stage, or comparative weakness, to the production of male 

 ones. 



Every one must have noticed that the cones of these trees are always on 

 the strong vigorous branches towards the top of the tree, or on the ends of the 

 strong laterals. Only this year did I observe that the male flowers are never 

 on these strong branches, seldom near the ends of the main shoots, but down 

 amongst the lowermost and weakest branches, and in the more interior parts 

 of the trees. 



My observations have been confined to Pi'wus and Thuja. I have examined 

 many hundreds of trees ; and so clearly does this law universally prevail, that 

 I am certain I have but to point it out in order to obtain a ready assent to it. 



The effects of vigor in bringing about these different sexual relations are very 

 interesting. Taking the Scotch, Austrian and Table Mountain Pines, which I 

 have had daily before me, the young shoot commences its axial growth early 

 in spring. Its base is the weakest part of it, being partially formed late in 

 the previous season, when vitality was about to take its annual rest. There- 

 fore, according to the laws of adnation or cohesion which I have before indi- 

 cated, there are no branches, but the leaves are mostly free, taking the form of 

 long chaffy scales. As the shoot grows it gathers strength, the leaves be- 

 come more and more adnate with the stem, and after a few inches of such 

 growth the branchlets in the shape of phylloid shoots or fascicles of " pine 

 needles '" appear. These gather strength as the shoot progresses, as shown by 

 their increasing length, until if the axis or shoot is very strong, a female cone 

 appears. The whole process exhibits a regularly increasing vigor, during 

 which the leaves are first suppressed, and ultimately both leaves, stem, and 

 axis with the culmination of vigor are suppressed or metamorphosed into a 

 female cone. 



Turning again to another and weaker branch, pushing forth into spring growth, 

 we find the base, instead of being bare of all except the free leaf scales, has 

 little conical heads of male flowers pushing from the axils of the leaf scales, 

 and which, if higher up, and when the shoot has attained more vigor, would be 

 phylloid fascicles. These male heads of flowers are evidently metamorphosed 

 branch fascicles, the first transformation of which commenced the year previ- 

 ous when active vitality was about to cease. It might occur here to inquire 

 why lingering vitality would not produce in the fall rudimentary changes of 

 the embryo fascicles at the base of the strong and ultimately cone-bearing 

 shoots, as well as the weaker ones'? This must be left to future examinations. 

 Possibly, to hazard a guess, strong shoots may have the power of more rapidly 

 maturing in the fall than the other ones. 



Another very interesting fact in connection with this subject is the loss of 

 power to branch, which the formation of male flowers induces. Taking a 

 branch of a Scotch Pine, if it lay not the foundation of a series of male 

 flowers in the fall, it will provide at least three smaller buds around one 

 stronger and central one, from which to make its axial growth next season. 

 But if these rudimentary male flowers are formed, no side buds appear; very 

 seldom at least do we find one weak spike along side the main and stronger one. 



What that force is which I have called vigor, or by what laws it is governed, 

 I do not pretend to say. I know it only by its effects. In the one case I see 

 a strong axial growth, associated with strong vigorous branchlets, and sup- 

 pressed foliage, culminating in the formation of female flowers ; on the other 

 hand I see a more weak axial development, associated with fewer cotemporary 

 axes, weaker branchlets and greater freedom of the foliage from cohesion, aud 

 together with this the production of male flowers. The law is apparent : the 

 nature of the law must be left to further explorers. 



[May, 



